Check out these amazing recordings of rain-drumming, beautifully explained in this video. I fell in love with the rain drumming recordings immediately and asked Tim, the recordist and producer, about the rules for working with them in the creation of new music. He replied that the short answer was yes, sent me the EULA, and wrote “My only (non-compulsory) request: I’d love to hear what you make!”.
Guitar + Rain. I’ll pursue it and see where that leads.